26 



ESSENTIALS OF BIOLOGY 



Glucose. 



CHO* — CHOH 



H-COH 



I 

 HOCH 



Fructose. 

 CH2OH CH2OH 



o 



HCOH — CH 



CHOH 

 CHOH 



CO* 



I 

 HOCH 



HCOH O HCOH 



(HO)C 

 HO-CH 



HCOH 



CHOH 



HCOH 



CH.OH CH.OH 



Oxide Ring 

 Formula 



Older Formula 

 * Aldehyde Group 



CH2OH 



Older Formula 

 * Ketone Group 



HCOH 



— CH2 



Oxide Ring 

 Formula 



This is the general type of structure, varied and extended in 

 almost innumerable ways. Among the carbohydrates are all the 

 sugars, starches, glycogens, celluloses, etc. 



Fats. Typical oils and fats are glycerides. Glycerol (or 

 glycerine) is an alcohol (that is, a carbon chain substance with 

 three of the hydroxyl groups, — OH) : it is 



CH2 — CH — CH2 



OH OH OH 

 " Fatty acids " are also long carbon chains which have the 

 terminal group — COOH. Thus stearic acid is 



CH3.[CHJi6.COOH 



Such an acid can attach itself to an — OH group in an alcohol, 

 by eliminating OH 3 from the attaching radicals, — OH (in the alco- 

 hol) and —COOH (in the acid). Thus tristearin (of mutton fat) is 



CH2 - O - CO - [CHslie - CH2 - CH3 



CH2 - O - CO - [CH^lie - CH2 - CH3 



CH2 - O - CO - [CH^lie - CH2 - CH3 

 Isomerism and stereoisomerism, (i) Consider the carbon chain 

 CH3 — CH2 — CH2 — CH2 — CH3 ; and transpose the C's, 

 with their attached H's thus — 



CH. 



CH. 



CH - CH2 - CH3 ; and again CH3 - C - CH; 



CH: 



CH. 



